3. In Use

To test Wi-Spy's performance, I set up a test WLAN consisting of a Linksys WRT54G and WPC54G client. I generated a nice, regular spectrum by running IxChariot's throughput script continuously sending data between the client and AP. I then loaded the Wi-Spy and Cognio hardware and software onto another notebook (which I'll refer to as the measurement notebook) and ran them simultaneously while moving around to a few of my standard wireless test locations.

Figure 4 is a cropped screen shot taken while the measurement notebook was sitting in Location 1, which is the same room as the wireless LAN that I had set up.

Figure 4: Wi-Spy and Cognio - Location 1
(click image to enlarge)

Both applications were set to show two traces - peak max and real-time data - and the difference is immediately apparent. Wi-Spy's real time plot (in yellow) appears to be coarser than Cognio's (also in yellow), which I suspect is due to a wider

Figure 5: Wi-Spy and Cognio - Location 2
(click image to enlarge)

Figure 5 shows that the peak level measured by the Cognio drops from around -75 dBm to about -90 dBm, while Wi-Spy shows a drop from -35 dBm to around -53 dBm. So while the absolute reference levels differ greatly, the relative levels seem to match pretty well with both products showing about a 20 dB drop in signal. Note also that I had to use Wi-Spy's maximum trace to make the previous determination; a technique that I found to be very useful.